One of the surprise highlights of Age of Ultron was the revelation that Hawkeye has a wife and children. It was an unexpectedly touching moment that helped to flesh out the character beyond "good at arrows" and "likes purple".
It was also fairly ironic considering that, in the comics, one of Hawkeye's main defining features is that he is a notorious ladies man. Over the years, the skirt-chasing marksman has had numerous flings with heroes like Black Widow and Spider-Woman and, apart from being briefly married to Mockingbird, has spent most of his career single and very much ready to mingle.
This difference can probably be chalked up to the movie version of Hawkeye borrowing a lot of elements from the Ultimate version of Clint Barton. In that continuity, Clint was a member of the Ultimates (that universe's version of the Avengers) and worked for SHIELD as a Black Ops agent. Like the movie version, this Hawkeye was also married and had two children.
Ultimate Hawkeye's family ended up getting murdered by Black Widow when she betrayed the team so maybe let's hope that the movies don't take too much from the Ultimate Comics.